23/11/06 1.4 GNSS APPROACH PROCEDURES

1.4.1 Usually, flying a basic GNSS non-precision instrument approach procedure is very similar to a traditional approach. The differences include the navigation information displayed on the GNSS equipment control and display unit and the terminology used to describe some of the features.

1.4.2 Flying a basic GNSS approach is normally point-to-point navigation and independent of any ground-based navaids.

1.4.3 GNSS procedures utilize a straight line (TO-TO) flight from waypoint to waypoint, as sequenced in the database. Slight differences between the published track and the track presented may occur. These differences are usually due to rounding of the track bearing and/or the application of magnetic variation.

1.4.4 The approach cannot be flown unless that instrument approach is retrievable from the avionics database which:

a) contains all the waypoints depicted in the approach to be flown;

b) presents them in the same sequence as the published procedure chart; and c) is updated for the current AIRAC cycle.

1.4.5 To ensure the correctness of the GNSS database display, pilots should check the data displayed as reasonable for the GNSS approach after loading the procedure into the active flight plan and prior to flying the procedure. Some GNSS avionics implementations provide a moving map display which aids the pilot in conducting this reasonableness check.

1.4.6 Pilots should not attempt to fly any approach unless the procedure is contained in the current navigation database. Flying from one approach waypoint to another waypoint that has not been loaded from a database does not ensure compliance with the published approach procedure. For the basic GNSS receiver, the proper RAIM alert limit will not be selected and the CDI sensitivity will not automatically change to ±0.6 km (0.3 NM). An FMC using GNSS may contain either the same RAIM alert limits as the basic GNSS receiver, or appropriate navigation performance indications and alerts for ±0.6 km (0.3 NM). For both basic GNSS and FMCs, manually setting CDI sensitivity does not automatically change the RAIM alert limit on some avionics implementations.

1.4.7 Approaches must be flown in accordance with the aircraft operating manual and the procedure depicted on an appropriate instrument approach chart.

1.4.8 Operators must be familiar with their State’s basic GNSS implementation procedures. The aircraft must have the appropriate avionics installed and operational to receive the navigation aids. The operator is responsible for checking NOTAMs to determine the operational status of the alternate airport navigation aids.

1.4.9 Procedures must be established in the event that GNSS outages occur. In these situations, the operator must rely on other instrument procedures. For installations where the FMC includes an AAIM capability, there may be no disruption to the operation unless the outage exceeds the FMC capability to sustain the required level of performance.

1.4.10 To begin the basic GNSS approach, the appropriate airport, runway/approach procedure and initial approach fix (IAF) must first be selected. Pilots must maintain situational awareness to determine the bearing and distance to the GNSS procedure IAF before flying the procedure. This can be critical to ascertain whether entering a right or left base when entering the terminal approach area in the vicinity of the extended runway centre line. All sectors and stepdowns are based on the bearing and distance to the IAF for that area, which the aircraft should be proceeding direct to, unless on radar vectors.

II-3-1-6 Procedures — Aircraft Operations — Volume I

23/11/06

1.4.11 Pilots must fly the full approach from the IAF unless specifically cleared otherwise. Randomly joining an approach at an intermediate fix does not ensure terrain clearance.

1.4.12 When an approach has been loaded in the airborne navigation database, the following actions are required. Depending on the GNSS equipment, some or all of the actions described below may take place automatically. Note that some FMC implementations do not conform to the display sensitivities discussed but instead provide comparable operations as described in the aircraft operating manual.

a) upon reaching a distance of 56 km (30 NM) to the aerodrome reference point, basic GNSS receivers will give either an “arm” annunciation or where the systems automatically arm the operation, an indication that the aircraft is in the terminal area;

b) at this annunciation, the pilot must arm the approach mode. Some, but not all, GNSS avionics implementations will arm the approach mode automatically;

c) if the pilot arms the approach mode early (e.g. where the IAF is beyond a range of 56 km (30 NM) from the aerodrome reference point), no changes to the CDI sensitivity occur until reaching a range of 56 km (30 NM). This does not apply to systems that automatically arm for the operation;

d) when both the approach mode is armed and the aircraft is within 56 km (30 NM) of the aerodrome reference point, the basic GNSS receiver changes to terminal mode sensitivity at 56 km (30 NM) and the associated RAIM setting. If the pilot fails to ensure the approach is armed at or before a range of 56 km (30 NM) from the aerodrome reference point, the receiver does not change to terminal mode, and obstacle clearance is not ensured. The obstacle clearance criteria assumes the receiver is in terminal mode, and the areas are based on this assumption;

e) on reaching a distance of 3.7 km (2.0 NM) before the FAF, and provided the approach mode is armed (which it should be, see item c) above), the CDI sensitivity and RAIM ramp to smoothly reach the approach values (0.6 km (0.3 NM)) at the FAF. In addition, the “approach active” annunciation will appear;

f) the pilot must check the “approach active” annunciator at or before passing the FAF and execute a missed approach if it is not present, or if it is cancelled by overriding an automatically selected sensitivity; and

g) if the CDI is not centred when the CDI sensitivity changes, any displacement will be magnified and give the incorrect impression that the aircraft is diverging further, although it may be on a satisfactory intercept heading. To avoid this phenomenon, pilots should ensure they are well established on the correct track at least 3.7 km (2.0 NM) before the FAF.

1.4.13 The pilot must be aware of the bank angle/turn rate that the particular GNSS avionics implementation uses to compute turn anticipation, and whether wind and airspeed are included in the calculations. This information must be in the manual describing avionics functionality. Over- or under-banking the turn onto the final approach course may significantly delay achieving course alignment and may result in high descent rates to achieve the next segment altitude.

1.4.14 Pilots must pay particular attention to the exact operation of the basic GNSS avionics implementations for performing holding patterns and, in the case of overlay approaches, operations such as procedure turns and course reversals. These procedures may require manual intervention by the pilot to stop the sequencing of waypoints by the receiver and to resume automatic GNSS navigation sequencing once the manoeuvre is complete. The same waypoint may appear in the route of flight more than once consecutively (IAF, FAF, MAHF on a procedure turn/course reversal).

Part II — Section 3, Chapter 1 II-3-1-7

23/11/06